Stereo problems

I recently put a new Stero in my car. a 98 neon. It was working great, then the radio wouldnt get power and was not turning on. I checked all the wiring and everything was ok. I checked the fuses and I blew my radio fuse. So I replaced it. Started working again and then yesterday it dies again. So I check no fuse is blown and my dash and ceiling light doesnt work. So I cant see at all at night so I can't drive. My question is why did the stereo die again? I called the company that makes it and they told me to exchange it at the store. So i did and this one doesnt work. Anyone might now what the problem is here?
Thanks Max

Bad connection. No ground for radio. Here's a wiring diagram.

I have a Diagram, thanks though. All wires are correct with the radio and the car. The ground is attached to the Chasis ground. The black wire. This wasnt a problem the first week I had it installed this all happend yesterday.